The desire for greater capacity integrated circuits (ICs) on smaller sized devices has increased interest in replacing today's 64 megabit DRAM with memory devices in the range of 256 megabit, 1 gigabit and higher. This need for increased capacity on the same or smaller substrate footprint device makes it necessary to replace conventional dielectric films previously used in stacked capacitor formation, such as silicon dioxide (SiO.sub.2), with dielectric films having higher dielectric constants. Capacitors containing high-dielectric constant materials, such as Ta.sub.2 O.sub.5, usually have much larger capacitance densities than standard SiO.sub.2 --Si.sub.3 N.sub.4 --SiO.sub.2 stack capacitors making them the materials of choice in IC fabrication. High dielectric constant films allow smaller capacitor areas which in turn enable closer spacing of transistors and increased transistor density. One material of increasing interest for stack capacitor fabrication is Tantalum Pentaoxide which has a relative dielectric constant more than six times that of SiO.sub.2. Accompanying the increased and expanding use of this material is a need for improved in-situ methods of removing unwanted deposits which accumulate within the processing chamber after repeated deposition cycles.
An available cleaning method involves the utilization of a remote plasma generator to produce reactive species which are delivered to the processing chamber. U.S. Pat. No. 5,449,411 issued Sep. 12, 1995, to Hitachi describes a process for cleaning a vacuum chamber prior to the deposition of SiO.sub.2 therein. A microwave plasma of process gases such as C.sub.2 F.sub.6, CF.sub.4, CHF.sub.3, CH.sub.6, F.sub.2, HF, Cl.sub.2 or HCl is described. The patent further describes that the cleaning process can be improved by applying an R.F. electric field to electrodes in the chamber.
U.S. Pat. Nos. 5,778,788 issued Aug. 4, 1998, to Applied Komatsu Technology, describes a method for cleaning a deposition chamber that is used in fabricating electronic devices by activating a precursor gas using a high power microwave source of between about 3,000 to 12,000 Watts or a power density in the remote chamber of about 12,000 Watts/liter to 48,000 Watts/Liter. The patent further describes a minor carrier gas such as Argon, nitrogen, helium, hydrogen or oxygen may be used to transport the reactive species to the chamber, assist in the cleaning process, or help initiate and or stabilize the plasma in the deposition chamber. The patent also describes the use of a chamber based excitation source used to further excite the reactive species provided to the chamber.
Another problem confronting the semiconductor industry is the increased cost to obtain process gases coupled with the increased costs of disposing of the exhaust by-products created by process gases. The cleaning gas NF3 is an illustrative example of this problem. Long recognized as a superior cleaning gas, the cost of purchasing NF3 has steadily increased. What is needed is an improved remote plasma chamber cleaning process which utilizes cleaning gases more efficiently resulting in an overall decrease in gas consumption. The improved process should rely solely on remote microwave excitation sources without requiring chamber based excitation to produce an effective plasma or remove chamber deposits. The decreased gas consumption lowers gas supply cost, CFC generation and gas disposal cost. More specifically, the improved method should be capable of providing commercially viable cleaning rates for dielectric films such as Ta.sub.2 O.sub.5.and other dielectric films.